1. Field of the Invention
The present invention relates to the treatment of ceramic fibers, and, more especially, to the treatment of ceramic fibers based on silicon nitride, silicon carbide or silicon carbonitride to enhance the surface properties thereof.
2. Description of the Prior Art
It is known to this art to prepare SiC or Si.sub.3 N.sub.4 ceramic fibers, or mixtures thereof, in particular from organometallic polymer precursors of such ceramic compounds.
These polymer precursors, as more fully set forth hereinbelow, are well known products which may be in the form of monomers, oligomers, cyclic or linear polymers, and also resinous polymers; they may be prepared by a wide variety of processes utilizing a wide range of starting materials.
According to a conventional process, these polymers (optionally after melting, if originally they are in the solid state) are processed into continuous filaments by any known means, in particular by extrusion through dies, and are then pyrolyzed (after an optional crosslinking to increase their high temperature strength) to yield the desired ceramic fiber final products.
It has been found, however, that the ceramic fibers based on SiC and/or Si.sub.3 N.sub.4 produced by this method may in certain instances have insufficient surface qualities. This may translate into an appreciable change in the overall performance of the fibers. By "surface quality", as utilized herein, is particularly intended the potential presence, on the one hand, of different chemical impurities, such as, for example, silica, and, on the other, of critical defects, which adversely affect the overall performance of the fibers in respect of certain mechanical properties, such as, for example, rupture or breaking strength.